ChemInform Abstract: Asymmetric Synthesis of 3‐Oxacarbacyclin and 3‐Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route.

Abstract

hormones hormones U 1000 31 -249 Asymmetric Synthesis of 3-Oxacarbacyclin and 3-Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route. -A new asymmetric synthesis of title compounds (XI) and (XIII), which are of medicinal interest, is presented. Key step is an enantioselective deprotonation of the prochiral ketone (I) with Li (R,R)-bis(phenylethyl)amide to the enol ether (III). -(VAULONT, I.; GAIS, H.-J.; REUTER, N.; SCHMITZ, E.; OSSENKAMP, R. K. L.; Eur.

Improved Synthesis and Isolation of Bedaquiline

“…Previous studies have indicated that the selectivity of the chiral Li complex, when using base 4a-b for deprotonation, can be influenced by the formation of mixed aggregates between LiCl, formed by the reaction of the respective lithium complex with 1, and 4a-b, which is more reactive and selective than the monomer or dimer of 4a-b. 31 Simpkins and Bunn reported a substantial improvement in the stereochemistry of chiral basemediated deprotonation reaction products with the presence of added LiCl. 32 There are several reports that generate the 4ab.LiCl mixed heterodimeric Li-amide/LiCl complexes, that is, either from the direct addition of LiCl to 4a-b or the addition of BuLi to the 4a-b hydrochloride salt.…”

“…32 There are several reports that generate the 4ab.LiCl mixed heterodimeric Li-amide/LiCl complexes, that is, either from the direct addition of LiCl to 4a-b or the addition of BuLi to the 4a-b hydrochloride salt. 21,31,33 Thus, in the next experiment, 4a was treated first with LiCl (2 equiv) to generate 4a•LiCl followed by the sequential addition of 1 and 2. In this case, the dr of the product changed to 45:55.…”

“…The salt was made according to the reported procedure. 31 To a solution of 4b• HCl salt (1.6 g, 2 equiv) in THF (20.0 mL), 5.61 mL of 1.6 M n-BuLi in hexane (9.2 mmol, 3 equiv) was added dropwise at −78 °C under the flow of argon. The solution was stirred for 10 min, warmed up to room temperature, and stirred further for 1 h. The clear yellow solution was recooled to −78 °C and again stirred for 1 h to form a pinkish solution of the chiral base complex.…”